For reference the MySubaru.com site (owner resource site) shows the Guaranteed Trade-in Value figure for my 2009 2.5X with manual transmission and 33,000 miles to be $12,850. This figure is what a Subaru dealer would guarantee as trade-in value on my car if I was to buy a new Subaru. It may not represent true wholesale value. Dealers usually only offer you Mannheim Auto Auction wholesale value for your region on your trade. I am mentioning the wholesale and trade buzzwords to show what absolute bottom dollar should be on my car as a comparison vehicle (base model 2.5X, 5-speed manual transmission). That should get you in a frame of reference for the car you are looking at and how it is equipped vs. mine.

As always, perform your due diligence, Carfax, etc. You can also get the VIN and take it to a Subaru dealer and have them run a Service History report on it. They usually do this for free. That would show any campaigns (recalls) that haven't been performed and also a history of any service/repair performed on the car by a Subaru dealer under warranty.